1. Field of the Invention
The present invention relates to an image forming apparatus of electrostatic recording system such as a copying machine and a laser beam printer and a method of forming an image for detecting an abnormal state thereof, and particularly relates to an image forming apparatus detecting a cause of image defect and a method of forming an image for detecting a cause of abnormality.
2. Description of Related Art
In the image forming apparatus of electrostatic recording system such as a copying machine, when a charge wire of an electrification charger charging a photoconductive drum is contaminated by toner or the like, a reduction in the charging ability or a charge unevenness takes place, resulting in a reduction in the image density or an image unevenness. Then, in the Japanese Patent Application Laid-Open No. 62-177571, an apparatus has been proposed which is provided with a sensor detecting the surface potential of the photoconductive drum, and cleans the charge wire when the charge unevenness is detected.
However, in the image forming apparatus of electrostatic recording system, unevenness of the formed image is caused not only by a trouble in the surroundings of the electrification charger as described above, but also, for example, by a trouble such as an abnormal state of a developing unit. When the image unevenness is produced, even if it is caused by a simple trouble, the user cannot find the cause of this trouble. Accordingly, the user cannot find the place to be checked, and cannot restore the apparatus to normal state unless he calls a serviceman. Also, for the serviceman, he needs much labor and time to find this cause.